JP4880761B2 - Data provision method - Google Patents

Description

  The present invention relates to a method for providing data and an associated apparatus. In particular, the present invention relates to a dual homing redundancy protocol implemented in a homing configuration that couples a first network to a second network. However, other than this is not excluded.

  VPLS (Virtual Private LAN Service) over Ethernet by establishing pseudowires between very many customer locations across the existing network over an MPLS (Multi-Protocol Label Switching) network ) Is common. This makes it possible to provide a multipoint-to-multipoint connection and simulate the presence of a LAN. As in any such network, it incorporates resiliency so that if a portion of the network fails, the rest of the network can adapt to this failure, thereby It is desirable not to isolate the customer who disconnects. In addition, during multicast or broadcast situations, packet loops (ie loops where the same packet is transferred indefinitely within the network without reaching the destination, thereby causing congestion) as well as frame It is a consideration of the latest network standards to reduce duplication (ie information that arrives twice at the destination device).

  Several homing configurations are known. “Single homing (single homing single connection (unprotected)” with a single connection between the provider edge (PE) node on the first network and the customer edge (CE) node on the second network (Also known as the name)), and the two homings of "single homing with link protection (also known as single homing dual connection)" and "dual homing" have two or more paths Provides resiliency in the network. In “single homing with link protection”, two or more paths are provided between the same CE node and PE node, whereas dual homing is realized by providing CE connected to two or more PEs. Thus, not only are two or more paths provided in case of failure on one path, but two or more PE nodes are provided in case of failure on one PE node. It has the advantage of being. Therefore, in such a dual homing configuration, a failure occurring in either the path or the PE node can be overcome by using the secondary path and the secondary PE node for data transmission.

  As can be easily understood, VPLS is a way to implement Level 2 VPNs within an MPLS network. When a CE node connected to a PE node is provided, the CE node can be either a customer (customer equipment) or a provider (eg an Ethernet network provider equipment in the case of an overlay network). ) Can be managed by either of the above. It is desirable that the customer does not need to manage or be affected by any impact on the status of the VPLS / MPLS network. This can affect the entire network.

  A network can be implemented using the Spanning Tree Protocol (STP) and its derivatives to prevent frame looping and provide resiliency to the network. However, if the interface is UNI (User to Network Interface), the provider will not be required to peer the CE node's Bridge Protocol Data Unit (BPDU), but will discard these data units. Or to transfer (tunnel) these data units as normal Ethernet service data units (SDUs) in the VPLS. Thus, if the customer can have an impact on the provider network, this can turn into undesirable behavior or network instability. Instead of the above, if the provider has full control over service control and provision of standby resources, it is possible to manage all OAM functions, and therefore more than not under the above control. Even better services can be provided to customers.

  As can be easily understood, the spanning tree protocol and its derivatives participate in the spanning tree in a dual homing configuration that should be considered in the event of any topology change and required in the event of any topology change. Network components (such as CE nodes and PE nodes) to do. Therefore, the general behavior of STP that breaks frame looping and duplication is not suitable for homing configurations, especially for dual homing configurations where one node, the CE node, cannot be excluded from decision making. Clearly it is not suitable. In addition, CE nodes controlled by customer equipment require BPDU communication through PE nodes, reducing valuable bandwidth in the path between PE nodes.

According to a first aspect of the present invention there is provided a method of supplying data from a first network to a second network, wherein first and second nodes are provided in the first network, and then These nodes have the ability to supply individual data to the second network. in this case,
i. At any one time, one of the first and second nodes provides data to the second network. Then
ii. When a failure is detected, the first and second nodes are configured to communicate with each other so that the other node can provide data to the second network.

  Such a method is preferred because it allows the first network to operate and provide resiliency to the second network without any influence from the second network when the first network is operating. It is.

  At least one of the first and second nodes, and more generally both nodes, can send query messages to the other of the nodes at any time. In general, a node that transmits a message waits for a predetermined time for a response from the other node. The effect of sending and receiving such a message is that it can be used to determine whether the other node is still functioning. That is, if a message is sent and no response is received, it can be inferred that the other node is no longer operational.

  Generally, one of these nodes is designated as a provisioning service node (PSN) and supplies data to the second network. That is, this node is in an active mode. The other node may be considered a standby node and generally does not supply data to the second network while the PSN is functioning. Such an arrangement is useful for preventing looping of data packets transmitted to the second network and duplication of the data packets.

  In general, if one of the nodes does not receive a response to the query message, the node that sent the message becomes the serving service node (PSN) and supplies data to the second network. If a node fails, such a method will help to ensure resiliency.

  Each of the first and second nodes generally transmits a communication to the other node when it determines that a failure has occurred in the path linked to the node connected to the second network. In the unlikely event that a path fails, such communication will provide resiliency.

  Each of the first and second nodes can become a supply service node upon receiving communication indicating that a path has failed. That is, when it is determined that a failure has occurred in a path linked to a node connected to the second network, the other node can be configured to automatically supply data to the second network. .

  Each of the first and second nodes is generally adapted to send a message across both ends of the first network when the node switches from the serving service node to the standby node. This method is convenient because it allows the first network to route data more efficiently than otherwise.

  The first and second nodes can be compatible. Such a method is convenient because it reduces the complexity of the first network. This is because it is not necessary to provide various types of nodes.

  According to the second aspect of the present invention, there is provided a network node comprising a receiver and a transmitter that respectively transmit and receive data traveling between the first and second networks that are nodes to which the node can be connected. Is done. This node has the function of receiving data from the first or second network via the receiver, to the other network of the first and second networks, or to the other network of the first and second networks. Has the function of transferring the data. Further, the node has a function of communicating with one or more other nodes by sending and transmitting communications. These communications are processed on receipt to determine whether data should be transferred between the first and second networks.

  Such a node can serve to provide resiliency to the connection of the second network with the first network.

  The node may be equipped with the ability to implement any of the optional features of the method according to the first aspect of the invention.

  According to a third aspect of the present invention, there is provided a network according to the second aspect of the present invention comprising at least two nodes configured to communicate with each other.

  A network according to the second aspect of the present invention is provided, in which two nodes are configured to communicate with each other to provide the method of the first aspect of the present invention.

  The network can be configured to provide a virtual private LAN service (VPLS). The network may be a multi-protocol label switching (MPLS) network, which tends to be connected as a mesh network. This mesh network makes the connection multipoint-to-multipoint.

  The node of the second aspect of the present invention can be considered a provider edge node. This provider edge node makes it possible to connect the second network. Accordingly, the provider edge node can be considered as a connection point or a coupling point between the customer network and the provider network.

  The link between the customer network and the provider network (ie, the attached network to the provider edge node) is generally not part of the MPLS network and is the only possible path between the customer network and the provider edge node Can only be provided.

  According to a fourth aspect of the invention, there is provided a machine readable medium having instructions therein, which when read on the machine, causes the machine to function as a node of the second aspect of the invention.

  According to a fifth aspect of the present invention, there is provided a machine readable medium having instructions therein, wherein when the instructions are read onto a machine, at least a portion of the method of the first aspect of the present invention is performed on the machine. To provide.

  Machine-readable media mentioned in any of the above aspects of the invention may include the following: floppy disk, CD-ROM, (-R / -RW, DVD ROM / RAM including + R / + RW, HD, and Blu-ray), and memory (including SD card, CompactFlash (registered trademark) card, XD card, memory itself, hard drive, Memory Stick (registered trademark)), tape , Any form of magneto-optical memory, transmission signal (including internet download signal, FTP transfer signal, etc.), wired line.

The present invention will now be described in detail by way of example only with reference to the accompanying drawings.
FIG. 4 shows a VPLS used by an embodiment of the present invention. FIG. 3 shows various “homing” configurations used in the prior art. It is a figure which shows the outline of a dual homing structure. FIG. 2 is a diagram illustrating an entire general finite state machine (FSM) of individual PE nodes. It is a figure which shows the finite state machine (FSM) of the apparatus of PE node which implement | achieves embodiment of this invention.

  FIG. 1 is a diagram showing a network in which a VPLS (virtual private LAN service) 100 is provided. The VPLS 100 may be provided on an MPLS (multi-protocol label switching) network or any other suitable network protocol (such as an IP network). The VPLS 100 includes a plurality of provider edge nodes PE (A to E). Each provider edge node PE communicates with each of the other provider edge nodes via pseudo wires 120. The provider edge node PE can be thought of as a connection point with the VPLS 100 for customers who want to transmit data across the network.

  The provider edge node and customer edge node may be any suitable device such as a switch, optical switch, router, and the like.

  The provider edge node PE also communicates with the customer edge node CE (1-8) outside the VPLS 100. The network is configured to allow data including broadcasted or multicast data to be transmitted across the VPLS 100 to individual customer edge nodes CE. As will be readily understood, the provider edge node PE that is part of the VPLS 100 can be controlled by equipment owned by the network operator. However, the customer edge node CE is generally not controlled by the network operator and is not a network connected to these customer edge nodes. Therefore, it is considered that control by a customer connected to the network is possible. In such an arrangement, the interface between the provider edge node PE and the customer edge node CE can be considered as a user-to-network interface (UNI). The VPLS network 100 can be thought of as a first network or provider network. The network connected to the customer edge node CE can be considered as a second network, that is, a customer network.

  In an alternative embodiment of the illustrated embodiment, the provider edge node can be configured to control the customer edge node CE and arbitrate the role of the customer edge node CE. In such an arrangement, if the network provider can also control the customer edge node CE, the interface between the provider edge node PE and the customer edge node CE is a network-to-network interface (NNI). Can think.

  As will be appreciated, resiliency can be ensured in several ways within the MPLS network using techniques available within the prior art. Therefore, this guarantee can be easily achieved in VPLS 100 as well. In contrast, the resilience between individual customer edge nodes CE and one or more connected provider edge nodes PE can be provided by several homing configurations described below.

  FIG. 2 is a diagram showing some of these configurations. A single homing 210 including one homing path 200 connects the provider edge node PE G and the customer edge node CE9. Such an arrangement does not provide resiliency. In this arrangement, if a failure occurs in the single homing path 200 or the provider edge node PEG, communication is lost between the VPLS 100 and the customer edge node CE9, so that any device connected to the VPLS 100 has data. Cannot be received.

  As an alternative configuration, single homing with protection 220 for link (s) can be used. This single homing comprises two or more homing paths 200, all of which are connected between one provider edge node PE F and one customer edge node CE10. Such an arrangement provides some resilience. That is, in this arrangement configuration, when a failure occurs in the single homing path 200, communication maintenance management between the VPLS 100 and the customer edge node CE10 is performed in the subsequent homing path 200. However, if a failure occurs in the provider edge node PE F, communication between the VPLS and the customer edge node CE10 is lost, so any device connected to the VPLS 100 receives data from the customer edge node CE10, and the customer Data cannot be transmitted to the edge node CE10.

  As another alternative, a dual homing 230 with two or more homing paths 200 can be used. Each of these homing paths connects the customer edge node CE11 with a different provider edge node, and in this case, PE H and PE I connect the customer edge node CE11 with the VPLS 100. Thus, a first node (such as PE H) and a second node (such as PE I) connect CE 11 to VPLS 100. As can be readily appreciated, such an arrangement can provide resiliency against homing path 200 failures, as in either the provider edge node PE H or PE I. . Although only two provider edge nodes are shown connected to the customer edge node CE11 in the figure, more provider edge nodes can be connected to the customer edge node CE11. For example, 3, 4, 5, 6, 7, 8, 9, 10 or more provider edge nodes can be connected to the customer edge node CE11.

  In this embodiment, the provider edge node PE is connected to the customer edge node CE using a dual homing configuration (such as a provider edge node) and either the other provider edge node in the dual homing configuration or the customer edge node CE It is configured to communicate with each other to detect a failure in any of the homing paths 200 with any of the provider edge nodes PE. In this arrangement configuration, the customer edge node CE does not need a configuration for recognizing a failure. The protocol used in such an arrangement can be considered a dual homing redundancy protocol (DHRP).

  If the provider edge node PE is configured to evaluate failures in either the provider edge node PE or the homing path 200, at least two modes of DHRP are possible. In the first of these modes (named “fixed role”), the provider edge node PE is any destination that is the connection destination of a provider edge node (which may be multiple provider edge nodes). To provide data to the customer edge node CE (that is, to provide a service) or to enter standby mode, so that data is not provided to any of the nodes to which the provider edge node is connected Configured to do either. When the provider edge node PE is in the standby mode state, the customer edge node CE receives the communication from another provider edge node PE that is not in the standby mode state (i.e., providing data), thereby VPLS100. Maintenance management of communication with the network. In the case of a failure related to the provider edge node PE providing the service, the node stops supplying data to the individual customer edge node to which the node is connected, and then the other node that has been in the standby state. The provider edge node PE provides data to each customer edge node to which the node PE is connected (the node PE provides a service).

  In another mode (named “base role per customer edge”), each provider edge node PE is in a standby state while the edge node is waiting for another customer edge node CE. It is configured to be able to provide services to one or more customer edge nodes CE. In this mode, the provider edge node PE can stop supplying data to some customer edge nodes while continuing to supply data to other customer edge nodes CE.

  Mixed homing path failure (ie, one failure between customer edge node CE and serving provider edge node PE, as well as another customer edge node CE and the other provider edge node PE in standby) The “fixed role” mode can be implemented more easily even if it cannot be resilient to one merger failure that occurs between them. On the other hand, although the role of the base for each CE is considered to require more calculation resources, it has resilience against the failure of the mixed homing path 200.

  In an individual DHRP deployment, data signals are transmitted between the associated provider edge nodes PE, thereby allowing the provider edge node PE to recognize and respond to the failure in the dual homing deployment. That is, the nodes in the DHRP arrangement configuration communicate with each other. Several such signals can be used, as described herein below.

Such signals include the following:
1. Hello message. This message can be considered as a query message, and is transmitted from time to time between the provider edge nodes PE, and is intended to confirm the failure of the provider edge node PE. In general, hello messages are transmitted at intervals, perhaps at approximately regular intervals.
2. Customer link status message sent from an individual provider edge node PE to the other provider edge node PE to indicate a failure of the homing path 200.
3. Topology change message issued from the provider edge node PE. This message changes service delivery to standby and is directed to all provider edge node PEs involved in the VPLS (related to individual VPLS) and refreshes based on elapsed time (optional behavior, It is intended to clear the MAC address entry in the form of a forwarding table without waiting for some applications such as video services to provide effective optimization). That is, communication indicating a change in topology is transmitted to the first network.
4). An APS message from a provider edge node PE to a partner provider edge node PE in the case of a forced command from a network carrier or a manual command.

  As will be readily appreciated by those skilled in the art, such message signals typically include a plurality of data. Table 1 details one example of the DHRP signaling message format of this embodiment when the Ethernet (registered trademark) layer is considered as a communication channel.

(Table 1): Signaling message format

The various fields in the message format are detailed below:
DMAC: Destination MAC address SMAC: Source MAC address Ether type (DHRP): DHRP Ethernet (registered trademark) type that uniquely identifies a DHRP frame.
Customer edge node CE ID: An 8-bit field that identifies “dual-homed customer equipment” that is of interest for protection. When “fixed role” is used, the value is 0x0x00. If "base role per CE" is used, the value ranges from 0x01 to 0xFF.
● OpCode: specifies the DHRP frame type. A DHRP frame containing an unknown OpCode is discarded without permission. OpCode can be set as follows for the signal detailed above:
○ Hello message: 0x01
○ Customer link status message: 0x02
○ Topology change message: 0x03
○ APS message: 0x04
○ Other messages, etc. ● OpCode-only field: If required by an individual message, further information can be carried in the format of a type length value (TLV) ○ Type: included in the value field An 8-bit field that specifies information. This field is in the range 0x00 to 0xFF. The types defined in this document are:
VPLS ID: 0x01 (used to identify the VPLS instance to be used in the topology change message)
-APS ID: 0x04
-Other types, etc. ○ Length: A 16-bit field that specifies the length of the value field. This field is in the range from 0x000 to 0x400.
○ Value: The variable length field contains variable information. For APS ID, the value field takes the following significant values:
・ 0x02: Forced switch ・ 0x01: Manual switch ● FCS: Frame checksum sequence

  FIG. 3 is a diagram showing an embodiment of the present invention, and DHRP is realized by this embodiment. In this arrangement, while the VPLS network operator (ie, provider) manages resiliency, the VPLS network 100 does not have any requirements regarding control or information of the customer edge node CE, but STP (Spanning Tree Protocol). Etc. can be activated.

  In this example, two homing paths 300 and 302 are provided to connect the customer edge node CE12 to two separate PE nodes (PE J and PE K). PE J connects to the customer edge node CE12 via the homing path 300, whereas the provider edge node PE K connects to the customer edge node CE12 via the homing path 302. Both the provider edge node PE J and the provider edge node PE K are connected via a pseudo wire 120 of the VPLS 100. Therefore, these edge nodes can communicate with each other.

  Each provider edge node (PE J, PE K) has the ability to communicate with both the first network (ie, VPLS 100) and the second network (ie, customer edge node CE12). Thus, each individual provider edge node will comprise a receiver a and a transmitter b that are capable of communicating with each of these networks. Each node also includes a processor c configured to process communications received by receiver a and to generate communications for transmission by transmitter b.

  Individual provider edge nodes PE can connect to any of the customer edge nodes CE at any point in time via an alternative homing path 200. That is, FIG. 3 shows only a single customer edge node CE12 connected to each of the provider edge nodes (PE J, PE K), but a plurality of customer edge nodes CE12 are connected to the provider edge nodes (PE J, PE J, PE K). It is also expected to be connected to each of the PE K). Similarly, the customer edge node CE can be connected to any number of provider edge nodes PE. As described above, when implementing such dual homing and DHRP, ie “fixed role” and “base role per customer edge”, two alternative configurations of provider edge node PE can be expected. As an example, the steps involved in DHRP used when considering the role of the base for each customer will be described in detail below with reference to FIG.

1. Either provider edge node PE that is desired to be used as a primary node is activated (this is the provider edge node of either PE J or PE K that performs communication in either of the homing paths 300 and 302). May be) In this example, PE J is assumed as the primary node. Therefore, the primary path for communication to the customer edge node CE12 is the path 300.
2. If a provider edge node failure occurs in PE J, the system restarts and automatically switches to using provider edge node PE K after node restart. In contrast, if a link fails in path 300, the system automatically switches to using provider edge node PE K and PE J enters standby mode.
3. Next, when data is being communicated to the customer edge node CE12 using the node PE K and the path 302, if a provider edge node failure occurs on the node side, this failure is caused by a time-out error from the “hello” message. As detected by the provider edge node PE J (ie, no response is received within a predetermined time). The provider edge node PE J then enters a standby state and communication is automatically switched to using the node PE J. Similarly, when a failure occurs in the path 302, this failure is detected by the provider edge node PE K. A “customer link status message” is then transmitted to the provider edged node PE J. This triggers a change of state, and then the provider edge node PE J begins to provide service. That is, this provider edge node PEJ becomes the primary node.
4). During communication, if either the provider edge node PE J or PE K goes into a standby state and then a failure occurs, node restart is initiated and then the system is reinitialized.
5. As in the above case, if a failure occurs in the provider edge node PE K or path 302, the system automatically switches to using the provider edge node PE J.
6). Manual and forced switch commands are also provided for maintenance purposes or for all other possible cases that may be required for the network provider to perform actions issued from the management system. .

  During the step, both the primary provider edge node (ie either PE J or PE K) and the standby node (ie one of provider edge node PE J or PE K) are probably protecting themselves in the MPLS network. Communicating with each other via the pseudo wire path 120, which is a resource that is managed. Each node is then configured to send “Hello” messages from time to time to determine whether the other PE node, PE J or PE K, is operating. This is done with a simple timeout. That is, if a response to the “hello” message transmitted by the provider edge node is not received by the provider edge node PE J or PE K within a predetermined time, it is assumed that a failure has occurred.

  Both of the provider edge nodes (PE J, PE K) can receive the "customer link" from the other provider edge node only when a failure occurs in the homing path 200 between the other PE node PE and the other CE node CE. "Status message" is also received; that is, if the path 300 fails, the provider edge node PE J sends a "customer link status message" to the provider edge node PE K. Similarly, when a failure occurs in the path 302, the provider edge node PE K transmits a “customer link status message” to the provider edge node PE J.

  To further highlight this, FIG. 4 shows a DHRP operating mode finite state machine (FSM), whereas FIG. 5 shows a provider edge node PE, in particular the provider edge PE J in the above example. It is a figure which shows the FSM process of. Table 2 below shows the state triggers used when using the FSM of FIG. 4, while Table 3 shows the state triggers used when using the FSM of FIG.

(Table 2): Status trigger for Figure 4

* ハローメッセージのタイムアウトによって検出されたもの
** 顧客のリンク状態メッセージによって検出されたもの
*** ノードの再開後 (Table 3): Status trigger for FIG.

* Detected by timeout of hello message
** Detected by customer link status message
*** After restarting the node

  As will be readily appreciated by those skilled in the art, in transport network terminology, the “manual” command allows state changes within the state machine if there is a fault related to the destination state. In contrast, the “force” command allows a state change even if a failure related to the destination state exists in the state machine.

  In the embodiment associated with FIG. 3, customer edge node CE12 is configured to receive data from both provider edge nodes (PE J and PE K). However, both nodes connected to the provider edge nodes (PE J and PE K) do not provide data at the same time. In fact, one provider edge node can be considered a serving service node (PSN), while the other provider edge node can be considered a standby node (SBN). Since the system is configured to configure one provider edge node first, the provisioning service node can also be considered an initialization node (IN).

  The property actions required by individual nodes are detailed below.

Supply Service Node (PSN)
Forward traffic (ie data packets) to / from customer edge node CE12. The customer edge node CE12 receives these data packets from the VPLS 100, and these data packets are sent to the customer edge node CE12.
-Send hello message to SBN / IN-Receive hello message from SBN-Receive customer link status message from SBN-Optionally, when changing SBN / IN status, all topology change messages in VPLS Send to PE

Standby node (SBN)
Discard traffic (ie data packets) to / from customer edge node CE12. The customer edge node CE12 receives these data packets from the VPLS 100, and these data packets are sent to the customer edge node CE12.
-Send hello message to PSN-Receive hello message from PSN-Receive customer link status message from PSN

Initialization node (IN)
Discard traffic (ie data packets) to / from customer edge node CE12. The customer edge node CE12 receives these data packets from the VPLS 100, and these data packets are sent to the customer edge node CE12.
-Wait for Hello message from PSN

  By using such a system, the provider edge node (PE J, PE K) can actively control the topology of the connection between the customer network and the provider network without being involved in the customer edge node CE12. Become. Therefore, in the present invention, the customer edge node adheres to the standard network, while the VPLS 100 adapts the resiliency taking into account the failure of the path 300, 302 or the provider edge node (PE J, PE K). Can be. Furthermore, as a protocol as described in detail, the resiliency can be managed without using an input signal from the customer edge node CE12, so that frame looping and duplication can be avoided without the requirement for realizing STP. Will be.

  As will be readily appreciated by those skilled in the art, the embodiments detailed above may be implemented in a manner such as the provider backbone transport (PBT) standardized by the International Telecommunications Union Telecommunication Standardization Sector ITU-T. It can be applied to any connection-oriented packet switched network (such as connection-oriented Ethernet®). In such a network, a communication channel can be used between two PE nodes.

  Embodiments of the present invention are also considered to provide a method of providing resiliency to a network connection between the first and second networks.

Claims (26)

A method of supplying data from a first network to a second network, comprising:
First and second nodes are provided in the first network, each having the ability to supply data to the second network;
i. At any given time, one of the first and second nodes supplies data to the second network;
ii. The first and second nodes are configured to communicate with each other via a pseudowire, so that if a failure is detected, the other node can supply data to the second network And detecting a failure by the communication between the first and second nodes,
iii. If each of the first and second nodes determines that a failure has occurred in a path that links the node to the second network, a message indicating that the failure has occurred in the path And transmitting to the other node for communication.   The method of claim 1, wherein at least one of the first and second nodes, generally both nodes, communicate at any time by sending a query message to the other node.   The node that has transmitted the message waits for a response to the communication from the other node before determining that a failure has occurred in the other node. Method.   4. The method of claim 3, wherein the node waits for a response for a predetermined time and then determines that the other node has failed if no response to the communication is received. .   The method according to claim 3 or 4, wherein the node starts supplying data to the second network as soon as it determines that the other node has failed.   As soon as the node starts supplying data to the second network, the node transmits a communication indicating that the supply of data to the second network is started to the first network. The method of claim 5.   Each of the first and second nodes starts supplying data to the second network in response to receiving the message indicating that a failure has occurred in the path. The method of claim 1.   As soon as the node starts supplying data to the second network, the node transmits a communication indicating that the supply of data to the second network is started to the first network. The method of claim 7.   The method according to any one of claims 1 to 8, wherein each of the first and second nodes is connected to a plurality of second networks.   10. The method of claim 9, wherein as soon as a node determines that a failure has occurred, it stops supplying data to all the second networks to which the node is connected.   10. The method of claim 9, wherein as soon as a node determines that a failure has occurred, it only stops supplying data to the second network where the failure is detected.   12. Three or more nodes communicate with each other, and each node in a communication state has a capability of supplying data from the first network to the second network. The method of any one of these.   13. The node not transmitting data to a second network is configured to discard data addressed to the second network received by the node. The method of any one of these. A network node,
A transmitter and a receiver that can transmit and receive data to and from the first and second networks, respectively, to which the network node can be connected,
A function of receiving data from the first or second network via the receiver and transferring the data to or from the other network of the first and second networks; And
Having a function of determining that a failure has occurred in a path linking the network node to the second network;
It further has a function of communicating with one or more other network nodes via a pseudo wire by sending and transmitting communication,
When the network node determines that a failure has occurred in the path, the network node transmits a message indicating that the failure has occurred in the path to the one or more other network nodes, and performs communication.
A network node, wherein the communication is processed upon reception to determine whether the data should be transferred between the first and second networks.   The network node according to claim 14, wherein the network node is configured to send a query message to another node as needed.   The system is configured to wait for a response to the query message for a predetermined time before it is determined that a failure has occurred in the node to which the query message was sent. 15. The network node according to 15.   The standby mode in which data intended for the second network received by the network node is not transferred to the second network is provided. Network nodes.   The active mode of transferring data intended for the second network received by the network node to the second network, according to any one of claims 14 to 16. Network nodes.   19. A network comprising at least two network nodes according to any one of claims 14 to 18 configured to communicate with each other.   20. A network according to claim 19, wherein two network nodes are configured to communicate with each other to provide the method according to any one of claims 1-13.   21. A network according to claim 14 or 20 configured to provide a virtual private LAN service (VPLS).   The network according to any one of claims 14 to 21, wherein the network is a multi-protocol label switching (MPLS) network.   The network according to any one of claims 14 to 22, wherein the network is a connection-oriented packet switching network.   The network according to claim 22, wherein the connection is multipoint-to-multipoint by being connected as a mesh network.   A machine-readable medium storing instructions that, when read on a machine, cause the machine to function as a node according to any one of claims 14 to 18.   14. A machine-readable medium having stored thereon instructions that, when read onto a machine, cause the machine to provide at least a portion of the method of any one of claims 1-13.

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